Evaporators and other heat-exchanger systems are in widespread use in an enormous variety of cooling, refrigeration, HVAC, and other applications in virtually every market and market sector ranging from residential, vehicular, commercial, to medical, scientific and industrial.
The most common type of conventional evaporators/heat exchanges is a fins-on-tube configuration (such as shown by way of example in FIG. 5). During normal operation, such evaporators accumulate frost on the surfaces of the fins and tubes over time which increasing restricts the airflow through the evaporator and decreases its performance.
As a result, evaporators must be subjected to regular defrost cycles (usually several times per day) to remove the undesired frost from the fins. A variety of defrosting techniques are well known in the art, most of which typically involve heating the evaporators over an extended period of time, either directly, or indirectly (e.g., by directing heated air or other heated gas over them). However, such defrost cycles are time consuming and thus also consume a great deal of energy and also produce undesirable heat within the space being refrigerated, such as a freezer compartment.
Accordingly, virtually all conventional evaporators have a low fin density to allow sufficient spacing between each fin so that frost would not completely block airflow through the evaporator before the next defrost cycle. However, a lower fin density also lowers the performance and efficiency of the evaporator.
In recent years, a new technology known as Pulse Electro-Thermal Deicing/Defrosting (PETD), has been successfully introduced and implemented in various defrosting applications. Specifically, PETD utilizes rapid resistive heating of particular element for fast and efficient defrosting thereof. However, in order for PETD to work properly, the working element to be defrosted must have a suitable minimum resistance value. But notwithstanding this requirement, the use of PETD in defrosting applications is particularly advantageous, because the lower overall energy usage/and much shorter duration of a PETD defrost cycle allows more frequent but efficient and energy-saving defrosting cycles, which enables PETD-equipped evaporators to be constructed with a greater fin density, and thus to be configured with a significantly lower volume than a corresponding conventional evaporator with similar cooling performance characteristics.
Unfortunately, while PETD can be readily utilized with specially constructed PETD-enabled evaporators, it is virtually impossible to use PETD with conventional fins-on-tubes evaporators/heat exchanges. This is because conventional fins-on-tubes evaporators/heat exchangers have an extremely low electrical resistance (e.g., 10 μΩ to 100μΩ). Such a low resistance value means that in order to utilize PETD therewith to heat the evaporator, extremely high electric currents would need to be applied thereto (e.g., 10,000 A would need to be applied to a 10μΩ resistance evaporator to generate a necessary value of 1 kW of heating power). Naturally, it is difficult and quite expensive to provide a power supply for the evaporator that is capable of delivering such a high current.
Even worse, the value of an inductive reactance of conventional evaporators exceed their electrical resistance by more than one order of magnitude. As a result, the voltage value required to induce the above-mentioned high current, is over 10 times than the value of voltage that would be necessary in the absence of that undesirable inductance.
Thus, it would be desirable to provide an evaporator/heat exchanger system based on a conventional fins-and-tubes design, but that is configured for advantageous utilization of inductive energy-saving rapid heating/defrost techniques. It would also be desirable to provide an evaporator/heat exchanger system based on a conventional fins-and-tubes design, that is optimized for use of inductive energy-saving rapid heating/defrost techniques therewith, but that is inexpensive, easy to manufacture, and that is capable of 1:1 replacement of correspondingly sized conventional evaporator/heat exchanger components. It would further be desirable to provide a method for modifying/reconfiguring a conventional fins-and-tubes evaporator/heat exchanger system, to optimize that system for utilization of inductive energy-saving rapid heating/defrost techniques (such as PETD) therewith.